Broadband communication systems comprise, in a typical configuration, a signal receiving station, such as a satellite dish antenna whose output is applied via optical fiber cables to a central office. Customarily, the central office (CO) has two or three outputs, one output being broadband signals in a frequency range of 50 to 600 Mhz for video and other broadband signals, for example, another output being narrow band, such as, for example, 5 to 30 Mhz for voice communications, a second broadband output of, for example, 500 to 750 Mhz. The actual frequencies and ranges depend upon the particular signals which each system is called upon to handle, and those given here are by way of example only. Signals in each of the three signal frequency ranges are usually transmitted over optical fiber cables to one or more nodes, in series or in parallel, each of which is located in the general vicinity of the region of end use. At each node the optical signals are convened to electrical signals and applied to a broadband coaxial cable trunk. The coaxial cable trunk is then tapped, at different points therealong, and the signals thereon are applied through a coaxial cable to a Network Interface Unit (NIU) which feeds the signals via distribution cables to the customer's premises. In present day systems, it is often necessary to amplify the signals on the coaxial cable received from the node and from the tap by the NIU, which requires a source of power for the amplifiers, and such a source is also required for other functions of the NIU. The AC power in the present day systems for broadband only networks is delivered via the coaxial cables. The power is supplied by power supplies connected to commercial power sources. The new networks will carry signals for a variety or services; i.e., broadband, narrowband, pots, etc. These new requirements created a need to develop a different approach to providing power to the various systems. This is due to the increased power consumption of the NIU and the current limitation of fifteen (15) amperes for most of the existing network components. Adding a parallel conductor either coax or copper to carry the additional power required is an expensive alternative but would resolve the power issues. A more cost effective and reliable approach is to install one cable capable of providing all electrical paths required by each component for proper network operation. This solution will also provide a network that is less susceptible to noise (hum modulation) caused by the AC power.
In such systems as described, it is generally highly desirable that the individual customers be able to communicate with the central office in order to request particular programming of, in particular, the video signal, such as pay TV or various types of subscriber add-ons ancillary to the broadband signal capability. To this end, the central office may have a manager module to which subscriber requests, usually narrow band signals, are directed, and a service module under command of the management modules for directing the appropriate programming or other requested services to the customer through the system. Thus, it is necessary in such a system that, in addition to the broadband and narrow band signals carried to the tap-off point, from the central office, that that portion of the system which extends from the tap-off through any amplifiers to the NIU and to the customer premises have a power capability and a voice capability. It is also desirable that there be test means extending back to the central offices for testing, for example, continuity throughout the system. Such a requirement is satisfied in present practice by separate cabling and wiring for each of the different needs, i.e., power, voice, and broadband. This is, relatively speaking, costly from an installation and material standpoint, and does not necessarily solve the aforementioned power supply problems.